The Peronosporales are an order

Order (biology)

In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 of water mould

Water mould

Oömycota or oömycetes form a distinct phylogenetic lineage of fungus-like eukaryotic microorganisms . They are filamentous, microscopic, absorptive organisms that reproduce both sexually and asexually...

s (Class Oomycetes) which can be pathogenic.


Many diseases of plants are sometimes classified under this order, but are sometimes considered members of order Pythiales

Pythiales

Pythiales is an order of water-molds . Some species of this order are the causative agents of several economically important plant diseases, such as Potato blight....

. Some of these pathogenic protists include the organisms responsible for potato blight

Phytophthora infestans

Phytophthora infestans is an oomycete that causes the serious potato disease known as late blight or potato blight. . Late blight was a major culprit in the 1840s European, the 1845 Irish and 1846 Highland potato famines...

, eucalyptus dieback

Phytophthora cinnamomi

Phytophthora cinnamomi is a soil-borne water mould that produces an infection which causes a condition in plants called root rot or dieback. The plant pathogen is one of the world's most invasive species and is present in over 70 countries from around the world.- Life cycle and effects on plants :P...

, sudden oak death

Sudden oak death

Sudden Oak Death is the common name of a disease caused by the oomycete plant pathogen Phytophthora ramorum. The disease kills oak and other species of tree and has had devastating effects on the oak populations in California and Oregon as well as also being present in Europe...

, and blue mold

Blue mold

Blue mold is a downy mildew disease of tobacco that is caused by Peronospora tabacina, a fungus-like protist in the family Peronosporaceae. Blue mold can cause severe damage to susceptible tobacco plants in many parts of the world...

. Further genetic studies may place these organisms more definitively in one order or another.